Read the docs
TI-2026-35872 Aliases CVE-2026-48512GHSA-cj9g-3mj2-g8vv

MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement

Priority LOW 28CWE-674Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Attack requirements
Present
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-674.

Summary

MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, MessagePack-CSharp's JSON conversion helpers contain multiple recursion paths that do not consistently enforce a depth limit. These paths are in the JSON conversion component rather than normal typed MessagePack deserialization. MessagePackSerializer.ConvertFromJson recursively processes nested JSON arrays and objects in FromJsonCore() without consulting MessagePackSecurity.MaximumObjectGraphDepth. TinyJsonReader.ReadNextToken() recursively consumes comma and colon separator characters, allowing even malformed JSON with long separator runs to consume one stack frame per character. MessagePackSerializer.ConvertToJson applies depth checks to arrays and maps, but the typeless extension branch for ext-100 recursively calls ToJsonCore() without applying MessagePackSecurity.DepthStep(ref reader). Each path can allow attacker-controlled input to exhaust the process stack and trigger an uncatchable StackOverflowException instead of failing with a catchable parse or serialization exception. This vulnerability is fixed in 2.5.301 and 3.1.7.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00405 35th percentileScored 2026-11-07
Fix Fixed MessagePack-CSharp (MessagePack-CSharp): 3.1.7, 2.5.301MessagePack (NuGet): 2.5.301, 3.1.7

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MessagePack-CSharpMessagePack-CSharp3.0 to before 3.1.7; before 2.5.3013.1.7, 2.5.301Patch availableCNA
—MessagePack (NuGet)before 2.5.3012.5.301Patch availableGHSA-cj9g-3mj2-g8vv
—MessagePack (NuGet)3.0 to before 3.1.73.1.7Patch availableGHSA-cj9g-3mj2-g8vv
  • MessagePack-CSharp VendorMessagePack-CSharp Affected 3.0 to before 3.1.7; before 2.5.301 Fixed in 3.1.7, 2.5.301 Patch available CNA
  • MessagePack (NuGet) Vendor— Affected before 2.5.301 Fixed in 2.5.301 Patch available GHSA-cj9g-3mj2-g8vv
  • MessagePack (NuGet) Vendor— Affected 3.0 to before 3.1.7 Fixed in 3.1.7 Patch available GHSA-cj9g-3mj2-g8vv

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:*before 2.5.301; 3.0.3 to before 3.1.7VulnerableMessagePack-CSharp
  • cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\#:*:* Versions before 2.5.301; 3.0.3 to before 3.1.7 Vulnerable ·MessagePack-CSharp

Remediation

  • Fix · CNA MessagePack-CSharp (MessagePack-CSharp) Fixed in 3.1.7, 2.5.301
  • Fix · GHSA-cj9g-3mj2-g8vv MessagePack (NuGet) Fixed in 2.5.301 Advisory →
  • Fix · GHSA-cj9g-3mj2-g8vv MessagePack (NuGet) Fixed in 3.1.7 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-48512
  2. 2026-10-03 Alias added: GHSA-cj9g-3mj2-g8vv

References

Advisory 2

Other 1

  • TI-2026-35549 MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input CVSS 3.1HIGH 8.2
  • TI-2026-35866 MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depth CVSS 3.1HIGH 7.5
  • TI-2026-35873 MessagePack-CSharp: DynamicUnionResolver generated deserializers miss depth enforcement CVSS 4.0MEDIUM 6.3
  • TI-2026-35863 Out-of-bounds read in MessagePack-CSharp CVSS 4.0HIGH 8.2
  • TI-2020-04290 Untrusted data can lead to DoS attack in MessagePack for C# and Unity CVSS 3.1MEDIUM 6.5
  • TI-2026-35877 MessagePack-CSharp: Typeless deserialization type restrictions do not recurse into arrays or generic arguments CVSS 4.0MEDIUM 6.3
See all 12 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences